Headgates are commonly used to restrain livestock, usually in conjunction with a squeeze chute or other type of containment pen, during inspection, branding, doctoring and other such animal handling activities. Various diverse types of headgates, squeeze chutes and containment pens are known in the livestock industry. The most commonly used headgates restrain an animal about its neck with either a set of swing doors that pivot in an out of a vertical plane or a pair of opposing stanchions that pivot within a vertical plane by means of a scissor action. Both types of headgates utilize substantially parallel upright metal posts to define the opening in which the animal's neck is confined when the headgate is in the closed position. Typically, the upright metal posts are bent to conform somewhat to the shape of the animal's neck.
It is desirable that the size of the opening for the animal's neck be adjustable to accommodate different types and sizes of animals. Presently, so far as Applicants are aware, such adjustment is achieved by varying the spacing between the upright posts, as illustrated in U.S. Pat. Nos. 4,771,737 and 4,302,908, or by employing a mechanism that surrounds the animal's neck, such as the headgate described in U.S. Pat. No. 4,059,073. It is also desirable to allow for adjustment of the shape of the headgate opening, that the adjustment mechanism be readily incorporated into the manufacture and assembly of the headgate and that the headgate be adaptable for use with a variety of different squeeze chutes and other livestock handling and containment pens. Further, the headgate can be utilized to its maximum advantage if it allows the operator to easily adjust both the size and shape of the opening in which the animal is confined.